GIFT  OF 


DEPARTMENT  OF  AGRICULTURE 

THE  UNITED  STATES  WEATHER 
BUREAU 


REPORT  PREPARED  FOR 

THE  COMMISSION  OF  THE  UNITED  STATES  OF  AMERICA 
TO  THE  BRAZIL  CENTENNIAL  EXPOSITION 


For  Distribution  at  the  Brazil  Centennial  Exposition 
1922-1923 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1922 


DEPARTMENT  OF  AGRICULTURE 


• 

THE  UNITED  STATES  WEATHER  BUREAU 


Supplementing  Exhibit 

of  the 
UNITED  STATES  WEATHER  BUREAU 

at  the 

BRAZIL  CENTENNIAL  EXPOSITION 

Rio  de  Janeiro,  Brazil 

1922-1923 


By 
DR.  C.  F.  MARVIN 

Chief  of  the  United  States  Weather  Bureau 


-   VTHE -UNITED   STATES   WEATHER   BUREAU. 

l£jj6  risgulat'  observing  stations  scattered  throughout  the  United 
States,  its  Territories,  and  the  West  Indies,  and  upon  similar  reports 
received  daily  from  points  in  other  parts  of  the  Northern  Hemisphere. 
Each  of  the  Weather  Bureau  stations  is  operated  by  one  or  more  trained 
observers,  and  is  equipped  with  mercurial  barometers,  thermometers, 
wind  vanes,  rain  and  snow  gauges,  anemometers,  and  sunshine  recorders ; 
also  barographs,  thermographs,  and  other  devices  which  make  continuous 
automatic  records  of  the  local  weather  conditions. 

The  results  of  the  twice-daily  observations  are  immediately  telegraphed 
to  the  central  office  at  Washington,  D.  C.,  and  other  forecast  centers 
where  they  are  charted  for  study  and  interpretation  by  experts  trained 
to  forecast  the  weather  conditions  expected  during  the  following  36  to  48 
hours.  A  complete  telegraphic  report  includes  the  following  data: 
Temperature,  pressure  (reduced  to  sea  level),  precipitation,  direction 
and  velocity  of  wind,  kind  of  weather,  clouds;  and  also  maximum  or 
minimum  temperature  since  last  observation.  From  these  data  the 
forecaster,  by  comparison  with  preceding  reports,  is  able  to  trace  the  paths 
of  storm  areas  from  the  time  of  their  appearance  to  the  moment  of  obser- 
vation and  approximately  determine  and  forecast  their  subsequent 
courses  and  the  attendant  weather  conditions. 

Weather  services  are  maintained  by  the  Canadian  and  Mexican  Gov- 
ernments, and  by  a  system  of  interchange  daily  reports  are  received 
from  a  number  of  stations  in  those  countries.  Daily  observations  are 
also  received  from  foreign  sources  so  that  the  field  represented  by  the 
daily  reports  extends  over  a  considerable  portion  of  the  Northern.  Hemi- 
sphere. By  means  of  the  extensive  survey  of  atmospheric  conditions 
afforded  by  these  reports  it  is  possible  to  forecast  important  weather 
changes  for  a  week  in  advance  with  a  fair  degree  of  accuracy. 

The  principal  stations  in  the  United  States  receive  reports  from  a 
sufficient  number  of  other  stations  to  show  the  general  weather  condi- 
tions over  a  considerable  portion  of  the  country. 

DISTRIBUTION    OF    FORECASTS. 

Forecast  centers  are  maintained  at  five  different  points  in  the  United 
States.  Within  two  hours  after  the  morning  observations  have  been 
taken  the  forecasts  are  telegraphed  from  these  centers  (see  map)  to 
about  i, 600  principal  distributing  points,  whence  they  are  further  dis- 
seminated by  telegraph,  telephone,  radio,  and  mail.  The  forecasts  are 
available  to  many  millions  of  people  within  an  hour  of  the  time  of  issue. 
This  system  of  forecast  distribution  is  wholly  under  the  supervision  and 
mainly  at  the  expense  of  the  Government,  and  is  in  addition  to  and  dis- 
tinct from  the  distribution  effected  through  the  press.  During  the  past 
few  years  the  rapid  development  of  radio  has  made  possible  a  much 
greater  distribution  of  the  daily  forecasts  than  heretofore. 


THE    UNITED   STATES   WEATHER   BUREAU.  3 

THE   WEATHER    MAP. 

Weather  maps  are  printed  at  many  Weather  Bureau  stations  and  mailed 
soon  after  the  morning  forecast  is  telegraphed.  On  this  map  the  impor- 
tant features  of  current  weather  conditions  throughout  the  country  are 
graphically  represented.  The  map  also  contains  temperature,  precipi- 
tation, and  other  data  from  observing  stations,  and  in  addition  a  brief 
statement  of  the  main  weather  features  presented.  In  order  that  all 
sections  of  the  country  may  receive  weather  data,  maps  or  bulletins  con- 
taining the  data  in  tabular  form  are  issued  from  most  of  the  larger  sta- 
tions. The  maps  issued  at  Washington  and  other  forecast  centers  con- 
tain detailed  forecasts  for  the  respective  forecast  districts,  while  other 
station  maps  and  bulletins  contain  forecasts  only  for  the  localities  in 
which  they  are  distributed. 

OCEAN  METEOROLOGICAL  SERVICE. 

The  ocean  meteorological  service  aims  to  collect,  through  the  coopera- 
tion of  vessel  masters  and  others,  meteorological  observations  at  sea.  It 
provides  blank  forms  for  reporting  these  observations,  collects  and  charts 
them,  reduces  them  to  average  values,  and  prepares  the  results  for  pub- 
lication on  the  ocean  Pilot  Charts  issued  by  the  Hydrographic  Office  of 
the  United  States  Navy. 

WEATHER  INFORMATION   BY   RADIO. 

The  recent  development  of  radio  has  made  possible  the  transmission 
of  meteorological  observations  made  by  ships  at  sea  to  shore  stations, 
thence  by  land  lines  to  a  central  meteorological  station. 

The  Weather  Bureau  has  organized  a  system  of  meteorological  obser- 
vations on  vessels  navigating  the  coastal  waters  of  the  Middle  and  South 
Atlantic  States,  the  Gulf  of  Mexico,  and  the  Caribbean  Sea,  the  primary 
object  being  to  gain  information  of  subtropical  storms  which  occasion- 
ally traverse  these  waters.  Observations  are  made  on  vessels  and  trans- 
mitted by  radio  to  shore  stations,  thence  to  the  central  office  of  the 
Weather  Bureau,  where  they  are  charted  and  used  in  making  forecasts 
and  warnings.  A  similar  service  is  also  maintained  on  the  Pacific  coast. 
Distribution  of  weather  information,  forecasts,  and  warnings  is  made 
daily  through  the  cooperation  of  the  radio  service  of  the  United  States 
Navy  and  other  interests.  (See  chart  of  distributing  stations.) 

CLIMATOLOGICAL   SERVICE. 

Although  the  regular  observing  stations,  each  representing  about 
15,000  square  miles  of  territory,  furnish  sufficient  data  upon  which  to 
base  the  various  forecasts,  observations  at  many  intermediate  points 
are  necessary  before  the  climatology  of  the  United  States  can  be 
properly  studied.  This  need  has  given  rise  to  the  establishment  of  an 
11279—22 2 


4  THE  UNITED  STATES  WEATHER  BUREAU. 

important  and  interesting  feature  of  the  Weather  Bureau  in  its  Clima- 
tological  Service,  which  is  divided  into  45  local  sections,  each  section, 
as  a  rule,  covering  a  single  State,  and  having  for  its  center  a  regular 
observing  station.  These  centers  each  month  collect  temperature  and 
precipitation  observations  from  more  than  4,500  cooperative  and  other 
stations,  and  each  publishes  a  monthly  and  an  annual  summary,  which 
gives  a  large  amount  of  climatological  data  for  its  section.  Throughout 
the  year  the  section  centers  receive  weekly  reports  of  weather  and  crop 
conditions  from  numerous  correspondents.  The  central  office  at  Wash- 
ington prepares  weekly  a  general  summary  of  weather  and  crop  condi- 
tions for  the  entire  country,  which  is  incorporated  in  "Weather,  Crops, 
and  Markets."  During  the  growing  season  in  the  cotton,  corn,  wheat, 
sugar,  rice,  broom-corn,  and  cattle-producing  sections,  designated 
centers  receive  telegraphic  reports  of  precipitation  and  daily  extremes 
of  temperature  from  substations  in  the  various  sections,  for  publication 
in  bulletin  form.  (See  exhibit  charts,  Special  Services.) 

MOUNTAIN   SNOWFAUv  MEASUREMENTS. 

Several  hundred  stations  are  maintained  in  the  elevated  mountain 
regions  of  western  United  States  for  the  purpose  of  obtaining  precise 
measurements  of  the  depth  and  water  content  of  the  snowfall.  Such 
measurements  are  useful  in  determining  approximately  the  amount  of 
water  available  for  irrigating  and  power  purposes. 

FORESTS   AND   STREAM    FU>W. 

A  special  study  to  determine  the  effects  of  forest  cover  on  the  flow  of 
streams  is  being  made  at  Wagon  Wheel  Gap,  State  of  Colorado,  in  co- 
operation with  the  Forest  Service.  Measurements  of  meteorological 
conditions  and  of  stream  discharge  in  two  forested  watersheds  have  been 
made  during  a  period  of  nearly  10  years.  The  relation  between  the 
two  streams  having  been  established  for  forested  conditions,  one  of  the 
watersheds  was  denuded  and  the  studies  continued  in  1920.  The  result- 
ing change  in  the  relation  between  the  streams  will  be  a  measure  of  the 
value  of  a  forest  as  a  controlling  factor  in  run-off. 

AEROIvOGICAL   INVESTIGATIONS. 

Free-air  observations  in  the  United  States  are  made  by  means  of 
kites  and  pilot  balloons.  The  kites  carry  meteorographs  which  record 
pressure,  temperature,  humidity,  and  wind  at  all  heights  reached.  The 
pilot  balloons  are  inflated  with  hydrogen  and  released,  and  their  move- 
ments through  the  air  are  followed  by  means  of  theodolites.  The  ob- 
served readings  of  these  movements,  together  with  the  known  height 
of  the  balloon,  make  possible  the  determination  of  wind  direction  and 
velocity  at  various  altitudes. 


THE   UNITED  STATES  WEATHER  BUREAU.  5 

The  results  of  these  observations  are  telegraphed  to  District  Forecast 
Centers,  where  they  are  used  in  preparation  of  forecasts  for  aviators. 
(See  Flying  Forecast  map.)  The  observations  themselves  are  later 
forwarded  by  mail  to  the  central  office  at  Washington,  D.  C..  where 
they  are  computed,  summarized,  and  studied. 

SPECIAL  PUBLICATIONS. 

Among  the  publications  of  the  Weather  Bureau  the  following  are 
worthy  of  special  notice: 

(a)  The  annual  report  of  the  chief  of  bureau,  including  a  full  summary 
of  climatic  data  for  the  United  States. 

(6)  The  Monthly  Weather  Review,  which  contains  elaborate  meteor- 
ological tables  and  charts  showing  the  weather  conditions  for  the  month 
over  the  United  States  and  neighboring  countries  and  papers  of  unusual 
interest  on  climatological  and  meteorological  subjects. 

(c)  Climatological  data  for  the  United  States  and  territories,   con- 
sisting of  monthly  and  annual  summaries  mostly  by  States,  and  con- 
taining charts  and  daily  climatological  statistics  of  temperature  and 
precipitation  for  the  entire  country. 

(d)  A  vast  amount  of  climatological  data  has  been  prepared  in  a  series 
of  separates,  each  treating  of  the  principal  climatic  features  of  a  limited 
area,  the  complete  set,  106  hi  all,  covering  the  entire  United  States. 

(e)  The  bulletins  and  Weather  Review  supplements,  published  occa- 
sionally and  now  numbering  about  70,  that  contain  the  larger  reports 
along  special  lines  made  by  the  experts  of  the  service. 

INSTRUMENTS  AND  APPARATUS. 

Accurate  observations  of  temperature,  rainfall,  and  atmospheric 
pressure,  etc.,  are  possible  only  by  aid  of  suitable  instruments  properly 
exposed.  The  kites,  meteorographs,  self -registering  instruments,  and 
other  forms  of  apparatus  devised  by  the  Weather  Bureau  are  known 
throughout  the  world.  The  present  perfected  equipment  has  been 
obtained  through  constant  endeavor  extending  over  a  period  of  nearly 
50  years. 

APPLICATIONS   OF   FORECASTS   AND  WARNINGS. 

The  extent  to  which  the  work  of  the  Weather  Bureau  affects  the  daily 
life  of  the  people  and  becomes  a  factor  in  their  various  vocations  and 
business  enterprises,  already  very  great,  is  increasing  yearly. 

Warnings  of  storms  and  hurricanes,  issued  for  the  benefit  of  marine 
interests,  are  the  most  important  and  valuable.  Storm  warnings  are 
displayed  at  more  than  300  points  along  the  Atlantic,  Pacific,  and  Gulf 
coasts  and  the  shores  of  the  Great  Lakes,  including  every  port  and  harbor 
of  any  considerable  importance ;  and  so  nearly  perfect  has  this  service 
become  that  scarcely  a  storm  of  marked  danger  to  maritime  interests 


6  THE  UNITED  STATES  WEATHER  BUREAU. 

occurs  for  which  ample  warnings  are  not  issued  from  12  to  24  hours  in 
advancer  The  reports  from  the  West  Indies  are  especially  valuable  in 
this  connection,  as  they  enable  the  bureau  to  forecast  with  great  accuracy 
the  approach  of  those  destructive  hurricanes  which,  during  the  period 
from  June  to  November,  are  liable  to  sweep  the  Gulf  and  Atlantic  coasts. 

Warnings  of  sudden  and  destructive  temperature  changes  known  as 
cold  waves  are  probably  next  in  importance.  They  are  issued  from  24 
to  36  hours  in  advance  of  the  cold  wave,  and  disseminated  throughout  the 
threatened  regions  by  all  the  means  quickly  available. 

Warnings  of  frosts  and  freezing  weather  are  also  of  immense  value, 
particularly  to  the  fruit,  sugar,  tobacco,  cranberry,  and  market  gardening 
interests.  The  truck-raising  industry  so  extensively  carried  on  in  the 
regions  bordering  on  the  Gulf  and  lower  Atlantic  coasts  and  which  has 
increased  so  greatly  in  recent  years,  is  largely  dependent  for  its  success  on 
the  cooperation  of  the  Weather  Bureau. 

In  the  citrus-fruit  districts  of  California  fruit  with  an  estimated  value 
of  $14,000,000  was  saved  by  taking  advantage  of  warnings  issued  by  the 
bureau  during  one  cold  wave. 

In  other  fruit  districts  growers  rely  largely  upon  the  warnings  of  the 
bureau  to  guide  them  in  smudging  and  heating  their  orchards  on  the 
occurrence  of  frost  or  freezing  weather  during  the  blossoming  period. 

RIVER  AND   FLOOD    SERVICE. 

Human  life  and  large  property  interests  along  the  rivers  of  the  United 
States  are  safeguarded  by  the  issue  of  flood  warnings. 

The  river  and  flood  service  is  organized  with  its  principal  headquarters 
at  Washington,  D.  C.,  and  subsidiary  district  centers  at  advantageous 
points  on  the  respective  rivers  along  which  a  service  is  maintained. 

Measurements  of  precipitation  on  the  headwaters  of  the  streams  and 
observations  of  the  height  of  water  on  the  gage  at  upstream  points  are 
collected  by  telegraph  or  telephone  from  substations  and  serve  as  the 
basis  for  warnings  of  floods  in  the  lower  reaches  of  the  streams.  Another 
useful  purpose  is  served  on  navigable  streams  giving  notice  of  boating 
stages  during  the  low-water  season. 

OTHER  BENEFITS  DERIVED  FROM  REPORTS  AND  WARNINGS. 

While  the  value  of  the  bureau's  assistance  to  many  interests  is  so 
obvious  as  scarcely  to  need  more  than  the  brief  mention  already  given, 
there  are  numerous  special  applications  that  might  not  have  been  sus- 
pected, a  few  of  which  may  well  be  noted  here. 

The  railway  and  transportation  companies  make  continued  use  of  the 
forecasts  in  all  of  their  shipments.  Perishable  products  are  protected 
against  temperature  extremes  by  icing  or  heating,  as  conditions  may 
require.  Shipments  of  perishable  goods  are  accelerated  when  it  is 


THE  UNITED  STATES  WEATHER  BUREAU.  7 

found  possible  to  carry  them  to  their  destination  in  advance  of  the 
expected  unfavorable  temperature  conditions,  or  they  may  be  delayed 
to  prevent  loss. 

The  uses  made  of  temperature  forecasts  in  the  cities  are  more  varied 
than  is  generally  supposed.  With  notice  of  an  approaching  cold  wave 
preparations  are  made  by  heating  and  lighting  plants  to  meet  the  in- 
creased demands  that  will  follow.  Plumbing  is  protected.  Street  rail- 
way companies  arrange  for  more  heat  in  their  cars.  Merchants  curtail 
advertisements  or  direct  attention  largely  to  cold-weather  articles.  Ice 
factories  reduce  their  output.  Charity  organizations  prepare  to  meet 
increased  demands  for  food  and  fuel,  and  thus  minimize  suffering  among 
the  poor. 

Frost  warnings  are  utilized  in  the  cranberry  regions  by  flooding  the 
bogs  until  after  the  cold  weather  has  passed  or  danger  of  frost  is  over. 
Many  crops  are  saved  by  being  harvested  in  advance  of  the  freeze.  Rain 
forecasts  are  utilized  to  enable  picking  or  harvesting  of  fruit  or  other 
crtfps  to  be  done  in  advance  of  rains.  City  departments  determine  the 
number  of  teams  needed  in  street  sprinkling;  railroad  companies  guard 
against  washouts;  and  irrigation  companies  control  the  output  of  water 
by  expected  conditions  of  rainfall  as  given  in  the  forecasts.  Warnings  of 
heavy  snows  are  valuable  to  railroads  by  enabling  them  to  organize 
their  snow-fighting  equipment  and  to  possibly  reduce  the  tonnage  of 
their  freight  and  passenger  trains.  On  the  great  western  ranches  and 
plains,  stock  is  hurried  from  the  ranges  to  shelter  upon  notice  of  blizzards, 
northers,  or  heavy  snows. 

Some  special  uses  of  the  storm  warnings  are  found  in  the  measures 
adopted  to  protect  property  and  crops  subject  to  inundation  from  high 
tides  or  backwater  blown  up  by  the  winds.  Vessels  load  hurriedly  to 
get  off  in  advance  of  unfavorable  winds. 

Flood  warnings  are  indispensable  to  river  industries,  and  to  operations 
carried  on  in  lowlands  subject  to  inundation.  Their  issue  is  followed  by 
the  removal  of  cattle  from  bottom  lands  and  by  the  saving  of  such  crops 
as  can  be  cut  before  the  high  water  reaches,  a  threatened  district.  Along 
the  river  streets  of  many  cities  the  basements  of  warehouses  and  other 
buildings  are  submerged  at  high  water;  accurate  river  forecasts  enable 
the  business  men  to  postpone  moving  their  goods  to  the  upper  floor 
until  the  last  moment,  and  often  prevent  the  needless  expense  of  such  a 
transfer  in  cases  where  it  is  known  that  the  flood  crest  will  be  below  the 
point  at  which  basement  stock  would  be  imperiled. 

The  daily  maps  and  bulletins  and  the  general  bulletins  and  reports 
containing  statistical  data  are  utilized  in  many  ways  by  the  public. 
Grain  and  cotton  brokers  are  guided  largely  by  the  forecasts  in  their 
operations.  Statistics  of  wind  pressure  and  direction  are  issued  in  the 
design  of  high  buildings  and  to  determine  the  origin  of  fires  resulting 
from  flying  sparks.  Humidity  records  are  used  by  silk  and  candy  manu- 


8  •      THE   UNITED   STATES   WEATHER  BUREAU. 

facturers,  in  tuberculosis  investigations,  and  in  studies  of  the  loss  of 
electric  current  in  high  voltage  transmission. 

Data  regarding  rainfall  and  snowfall  are  extremely  useful  in  planning 
irrigation  enterprises  and  selecting  reservoir  sites,  and  are  studied  in 
connection  with  the  construction  of  water  works,  bridges,  culverts,  and 
sewers. 

Climatological  data  are  used  in  scientific  studies  of  the  relation  of 
weather  to  health,  life,  and  human  pursuits ;  by  railroad  companies  in  the 
adjustment  of  claims  and  demurrage  charges;  by  homeseekers;  by  inva- 
lids in  search  of  health  resorts;  by  irrigation  investigators;  by  contractors 
and  builders  in  settling  labor  accounts;  by  merchants  in  studies  of  the 
relation  of  the  weather  to  their  daily  sales;  as  adequate  testimony  in 
court  proceedings;  in  dry-farming  investigations;  in  studies  of  soil  culture, 
practical  agriculture,  and  the  life  and  migration  of  insect  pests;  in  plans 
for  the  development  of  the  arid  regions;  in  the  preparation  of  historical 
records;  by  bond  and  investment  companies  in  determining  the  loan 
values  of  farm  lands  in  newly  opened  countries ;  in  short,  in  nearly  every 
calling  in  which  the  weather  plays  any  part. 

THE   EXHIBIT. 

The  charts  and  pictures  are  arranged  according  to  the  following  plan: 

In  the  center  are  shown  the  means  by  which  weather  reports  are  col- 
lected and  the  forecasts  distributed,  the  radio  being  featured.  Copies  of 
charts  actually  used  in  forecast  work  are  exhibited. 

Four  additional  groups  of  charts  and  pictures  illustrate  the  character 
of  the  principal  services.  In  the  upper  right-hand  corner  the  river  and 
flood  service,  below  that  the  special  services ;  in  the  upper  left-hand  cor- 
ner, the  use  of  the  general  wind  and  weather  forecast,  below  that  the 
storm-warning  and  hurricane  service. 

Other  groups  indicate  the  nature  of  the  aerological  and  the  instrument 
work;  and  for  general  interest  there  are  cloud  charts,  illuminated  pic- 
tures, climatological  charts,  and  maps  showing  storm  movements. 


LD  21-100m-12,'43  (8796s) 


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